The air separation distillation column is the core equipment of the air separation unit. It is mainly based on the physical properties of oxygen, nitrogen, argon and other air components with different boiling points. Through multiple evaporation and condensation processes, it can realize the efficient separation and purification of air. It is the key process to produce high-purity oxygen and nitrogen.
The air separation distillation generally adopts the double tower distillation structure, which is divided into the upper tower and the lower tower, and works together with the main cooling heat exchanger. After purification and cooling, the low-temperature compressed air enters the distillation column. On the tray or packing in the column, the low-temperature rising gas fully contacts with the low-temperature reflux liquid from top to bottom, and heat and mass transfer exchange occurs. Among them, nitrogen with lower boiling point is easier to vaporize and rise, and accumulate in the upper part of the tower; Oxygen with higher boiling point is easier to liquefy and settle, and is enriched in the lower part of the tower.
The lower column mainly completes the preliminary separation of air to produce pure liquid nitrogen and oxygen enriched liquid air, providing stable raw materials and reflux cold source for the upper column distillation. The upper tower relies on the materials transported from the lower tower for further deep rectification, and high-purity nitrogen and oxygen are separated through continuous gas-liquid exchange. The main cooling heat exchanger plays the role of core heat exchange, realizing the condensation of rising steam and the vaporization of reflux liquid, and continuously maintaining the equilibrium condition of distillation in the tower.
The whole distillation process relies on the continuous circulation of gas-liquid two-phase exchange without chemical reaction. It is purified repeatedly through physical phase change, and finally produces oxygen and nitrogen products that meet industrial standards. It has the characteristics of continuous operation, high separation accuracy and strong stability.
